#version 120 

uniform sampler2D velocities;

void main(){
	
	vec3 newVelocity = texture2D (velocities, gl_TexCoord[0].xy).xyz;
	
	// add gravity
	newVelocity += vec3(0,-2,0);
	
	gl_FragData[1] = vec4(newVelocity, 1);
}